1. Field of the Invention
The present invention relates to disk drives and particularly to a load beam design that prevents damaging contact between a magnetic head slider and a magnetic medium due to shock loads applied to the disk drive. More specifically, the present invention relates to a load beam design for use with a flex circuit to limit the separation of the slider and the flexure from the load beam during a shock event, in order to increase the disk drive tolerance to shocks.
2. Description of Related Art
In a conventional disk drive, a read/write head is secured to a rotary actuator magnet and a voice coil assembly by means of a suspension and an actuator arm, and is positioned over a surface of a data storage disk. In operation, a lift force is generated by the aerodynamic interaction between the head and the disk. The lift force is opposed by a counteracting spring force applied by the suspension, such that a predetermined flying height is maintained over a full radial stroke of the rotary actuator assembly above the surface of the disk.
The suspension includes a load beam, a flexure secured to a cantilevered end of the load beam, and a slider resiliently mounted on the flexure. In order to permit pitch and roll movement of the slider to follow the disk surface fluctuations, the flexure is typically provided with a cantilevered tongue which is resiliently secured to the remainder of the flexure, and to which the slider is mounted. A dimple extends from either the load beam or the flexure tongue, to provide a point load about which the slider gimbals.
With the disk drive industry's heightened demand for increased robustness and tolerance to shock loads, it has become necessary to minimize damaging contact between the head slider and the disk, and also to prevent permanent deformation of any part of the suspension as a result of a shock load.
Mechanisms have been proposed for limiting the movement of the flexure for protection against damage under shock load conditions. One such mechanism is disclosed in U.S. Pat. No. 4,724,500 to Dalziel that describes a limiter that includes a pair of wing elements mounted on an opposite pair of raised shoulders of the slider assembly and an elongated support element mounted on the arm and terminating in an end portion disposed between the opposite wing elements and a central portion of the slider assembly, to limit the downward motion of the slider assembly away from the arm and the rotational motion of the slider assembly relative to the arm. This motion limiter structure is rather complicated in that an assembly of components is required, including the specially designed slider, and in that the structure adds significantly to the weight, height and difficulty of manufacture and assembly of the suspension. The added structure would be particularly undesirable in the design of smaller suspension assemblies.
Another motion limiter is disclosed in U.S. Pat. No. 5,333,085 to Prentice et al. that describes a tab which is attached to the head/slider assembly, such that when the gimbal is assembled to the load beam, the formed tab passes through an opening created for this purpose in the load beam, and extends beyond the opening far enough to prevent its returning through the opening after the gimbal and load beam are spot welded together. The tab/opening arrangement is such that shock forces will result in contact between the tab and the sides of the opening in the load thus preventing excessive motion of the gimbal. The Prentice et al. motion limiter requires special manufacturing and assembly steps. To assemble the flexure to the load beam, the tab must first be moved through the opening and then the flexure needs to be longitudinally shifted relative to the load beam to its mounting position. Moreover, the tab formation comprises multiple bends, the degree of each bend being critical in the definition of the spacing between the tab and the stop surface, and errors in the formation of the bends can significantly affect the ultimate spacing of the stop mechanism. Thus, the forming operation must be precisely controlled and monitored.
A further motion limiter is disclosed in U.S. Pat. No. 5,771,136 to Girard, which is incorporated herein by reference, and which describes a flexure having a cantilever portion provided with an integral limiter and stop surface. The limiter can be connected with the flexure by a 90-degree bend. The movement of the free-end of the cantilever portion in one direction will cause the limiter engagement surface to contact the stop surface of the flexure.
None of the conventional motion limiters described above specifically addresses the design concerns associated with the use of a flex circuit or flex circuit on suspension (FOS). K.R. Precision proposed a head design incorporating the FOS on one side of the suspension, along the central axis of the load beam, with conductive traces bent for connection to the slider. However, this routing of the FOS on the load beam seems to require a special suspension design, and might not provide suitable motion limiting function when is use with commonly available suspensions such as the Hutchinson 2030 type suspension.